The Untold Truth Of Lemons

There are few fruits that are as versatile as lemons. They work in sweet and savory dishes, in drinks, desserts, and especially over fish. And they've been around for a long, long time. 

According to National Geographic, researchers have used the DNA of today's citrus fruits to trace them back to some time in the late Miocene epoch... but what the heck does that mean? That means wild citrus trees have been growing for around seven to eight million years. 

The BBC says those original trees came from the foothills of the southern Himalayas, and it wasn't until the weather shifted and became drier that they began to spread. That was about four million years ago, and since that spread we've cultivated today's fruit. Lemons are descended from the citron, the sour orange, and the pomelo, and from the very moment mankind first bit into one, they were special. Lemons were especially prized by the ancient Romans and other Mediterranean peoples, who considered them a valuable commodity for their rarity, exoticism, and their usefulness, both practical and symbolic (via LiveScience).

And things haven't changed too much. We still value these deliciously sour fruits, and it turns out there's a lot of fascinating things you might not know about them.

Scurvy is a very olde-timey sounding name for a disease that's caused by a vitamin C deficiency, and it's horrible. Without getting into too many gory details, Healthline says that vitamin C is essential for the production of collagen, which holds the body's tissues together. When a person doesn't get enough, scurvy sets in — and brings along horrible things like skin, eye, and mouth hemorrhages, internal bleeding, tooth decay, and other equally terrible things. 

According to the BBC, men sailing the seven seas up through the 18th century were particularly susceptible to the disease, as they would often spend months on a ship with no real, fresh food to speak of. Entire crews of hundreds and hundreds were struck down by the rotting disease, and it wasn't until 1747 that James Lind discovered that lemons — and oranges — wouldn't just prevent scurvy, but cure it. 

Later, the British Navy ordered hundreds and thousands of gallons of lemon juice for their ships, and scurvy was nearly eliminated. And National Geographic says it changed history, giving the British Navy the full complement of men they needed in order to stop Napoleon. Even today, the symbol of the Institute of Naval Medicine is a lemon tree.

It takes a certain kind of palate to be able to bite into a lemon, but here's a little fun fact: according to National Geographic, the pH of the typical lemon is between two and three, and that means they're on the same part of the sourness scale as a dill pickle. Neat, right? 

That pH value is what makes lemons taste sour, and without getting into science that's too complicated, here are the basics. According to the Australian Academy of Science: "Acidity is a measure of the concentration of hydrogen ions present when a substance is dissolved in a liquid." The more hydrogen it releases, the more acidic it is — and a lemon is surprisingly acidic. 

The pH scale ranges from one to 14, with items rated at one being the most acidic. Pure water is a true neutral, with a value of seven. For some more perspective, vinegar is a three, cola is slightly more acidic at 2.5, and battery acid is a one. 

But there's more to it than that. According to researchers from the University of Amsterdam (via Science), when things start getting too acidic, it starts interfering with cell function. Biology had to find something of a work-around, and that's the ability to push acidic substances into what's basically solitary confinement inside the cell. These pumps work overtime in lemons and other sour fruits, and weirdly, they're also pretty active in certain flowers and have been linked to the same function that gives, for example, petunias their red color. Weird? Absolutely.

There's a weird belief floating around that lemons are so acidic that they can actually cook beef. That's just not true: SFGate says that if you try to eat beef "cooked" with lemon juice, there's a good chance you're going to get sick because it's not actually capable of raising the temperature of beef to a level deemed safe. 

But when it comes to beef, lemon has some even stranger properties. If you add lemon to a marinade, you're not just changing the flavor of it, you're actually tenderizing it, too. 

Fine Cooking says that marinating meats in a highly acidic solution — like a lemon-based one — will cause a reaction where protein bundles start to break down and the meat will become more tender. But there's a catch: if you marinate for too long in that same acidic solution, it will make the meat tougher. Your best bet for beef is to cut it into small cubes and give it just a short rest in the marinade. No overnight prep needed for this one!

First, the good news: lemons are good for you. According to Healthline, there are a ton of great reasons to add them to your diet. They're a great source of vitamin C that has been shown to reduce your risk of stroke and heart disease), and regularly eating citrus fiber has been found to lower cholesterol levels. Citric acid has been linked to lessening the frequency of kidney stones in some studies, and lemons also help prevent iron deficiency. They don't contain much iron themselves, but they do make your body more efficient at absorbing what you get from other foods. They've also been linked to helping prevent certain types of cancers, and aiding in weight loss, but more studies are needed there for some conclusive evidence. 

Now, the bad news. Too many lemons can have some negative effects, says Insider. That includes the erosion of the enamel of your teeth, making canker sores worse, and it might upset your digestive tract. Citrus fruits and lemons are a known migraine trigger for many people, as well, so it pays to be aware of how you're feeling after adding a squeeze of lemon juice to your water or a slice to your drink. 

You've probably seen someone posting on Facebook that you should put a slice of lemon on your nightstand. It seems really unlikely that it's going to actually do anything, but this modern trend has roots in aromatherapy practices. 

According to The Times of India, there's a whole slew of benefits that come with breathing in the pleasant smell of a fresh lemon every night. The strong scent is believed to help clear the nasal passages, and it's thought to be particularly helpful to those with asthma or other respiratory issues. It's also been credited with helping to control headaches, decrease stress and anxiety levels, and increase the amount of serotonin in the brain (that's the happiness chemical that is crucial to a balanced mood). It's even been suggested that it can help regulate blood pressure. 

Doubtful? There are other benefits that even the most cynical non-believer will admit might just make it worthwhile to stock up on lemons. Not only does the strong smell of a cut lemon act as a natural air freshener, but it'll also help keep mosquitoes and ants away. Remember that for your next camping trip!

If you never wrote secret messages when you were a kid, you were seriously missing out. And here's a fun fact you can pass on to your own kids: lemon makes a brilliant invisible ink. 

According to National Geographic, all you need to do is use the lemon juice as ink to write on the paper. Let it dry. Then, the recipient just need to hold it (carefully) over a heat source to reveal the message. It works because the acid nature of the lemon juice weakens the fibers that make up the paper, so when they're exposed to the stressor of heat, they change color first. 

If you care to try it, you'll be doing a fun little experiment that has been very serious at times. Renaissance artists were fond of using lemon juice when they needed to write something they wanted to keep secret, and wartime spies have used it for a long, long time. Lemon juice correspondence was used in wars from the American Revolution all the way up to World War II. During World War I, the British captured an entire group of spies — known as the "lemon juice spies" — who were using the technique to get information back to Germany, and the British National Archives even still has one of the lemons seized from one of the German spies. Who would have thought the lowly lemon would have been so important to the war effort?